fun, press tab, modern IDE fills in the remaing function characters.

Unfortunately we keep designing languages for people using notepad.

Nowadays my editor even writes full blocks at a time.

If "fun" and "func" are already "not great" (because, I presume, they're too long), then "fun[TAB]" is not the solution.

Mind you, I'm not saying that your solution doesn't work. Just that it doesn't work for the GP.